The present invention relates to a method of controlling detonators fitted with integrated electronic delay ignition modules, as well as to an encoded firing control unit and encoded ignition modules for implementation of the method.
In most operations dealing with explosives, the detonation of the charges is triggered according to a precise time sequence, in order to improve the working yield of the explosive and to control its effects better.
Conventionally, the various delay times between the explosions of the charges are obtained according to a pyrotechnic process at the level of the detonators themselves. The detonators are initiated simultaneously by an exploder which delivers a certain electrical energy in a line of fire which connects the detonators in series or in parallel.
However, the pyrotechnic delay generated by the combustion of a delaying pyrotechnic compound exhibits a relative accuracy sometimes insufficient for some applications.
In order to remedy this short-coming, it has been suggested recently to use electronic-type integrated delay detonator ignition devices, which enable making the most of the accuracy achievable in electronics to enrich and fine-tune the delay time ranges that could be obtained in a pyrotechnic way. It has been suggested in the U.S. Pat. No. 4.674,047, as well as in an article covering a conference held by the inventors about the same topic "The Development Concept of the Integrated Electronic Detonator--Worsey-Tyler--Society of Explosives Engineers--Proceedings of the 9th Conference of Explosives and Blasting Techniques--1983 Jan. 31 -Feb. 4" to resort to detonators fitted with electronic means enabling them to communicate with an external control unit. Every detonator has a capacitor whose discharge actuates the explosive charge. The delay times of every detonator can be programmed on site, an identifying code having been assigned to every detonator previously, for instance in the factory. During a firing sequence, the detonators receive orders from the firing control unit, to load the capacitor specified, then to fire. It sends information back to the firing control unit, enabling the control unit to control the correct operation of the firing sequence. To this end, the detonators are fitted with an on-board microprocessor-based intelligence. The delay times programmed are stored on non-volatile memories.